Synthesis of carboxyl functionalized microporous organic network for solid phase extraction coupled with...

In this work, the carboxyl functionalized microporous organic network (MON-COOH) was synthesized as an efficient adsorbent to fabricate solid phase extraction (SPE) column for the extraction of p-nitrophenol, p-chlorophenol, 2,6-dichlorophenol and 2,3-dichlorophenol from water samples, followed by their analysis with high performance liquid chromatography (HPLC). The obtained MON-COOH was characterized with solid ¹³C nuclear magnetic resonance spectroscopy, fourier transform infrared spectroscopy, thermogravimetric analysis, N₂ adsorption-desorption isotherms, scanning electron microscope and water contact angle experiments. The integrating of carboxyl groups into aromatic MON's networks led to their good enrichment for the studied phenols. The hydrogen binding, π-π and hydrophobic interactions played key roles during the extraction. Effects of adsorbents type, desorption solvent and volume, pH and ionic strength were studied. Under the optimal extraction conditions, the MON-COOH column for SPE coupled with HPLC for the determination of the selected four phenols gave the linear range of 0.5-1000 μg L^-1, the limit of detections (LODs, S/N = 3) of 0.13-0.62 μg L^-1, the limit of quantifications (LOQs, S/N = 10) of 0.43-2.06 μg L^-1, the enhancement factors of 113-216, and the intra-day, inter-day and column-to-column precisions (relative standard deviations, RSDs) of 2.8-6.1, 4.1-8.7 and 6.7-10.3%, respectively. The developed method was successfully applied to the analysis of phenols in wastewater samples with the recoveries of 80.3-99.5%. These results revealed the potential of functional MONs as efficient adsorbents in sample pretreatment.